A backlight module is an optical device for providing a backlight source in a LCD product. A conventional backlight module includes a light source, a light-guiding plate, an optical film, and a plastic frame. The backlight source can be realized as an electro-luminescence (EL) device, a cold cathode fluorescent lamp (CCFL) device or a light emitting diode (LED) device.
The EL device and LED device are usually used in small-sized and mono-color (green or red lights) LCD products. Although some LCD products use white light (panchromatic) EL device or LCD device as backlight source, the LCD products with EL device or LCD device are only small-sized LCD (e.g. cellular phone, PDA, Gameboy) because the illuminations of EL device and LCD device are lower than which of the CCFL device. Therefore, the large-sized LCD products commonly use the CCFL device as white light backlight source due to the higher reliability and stability.
U.S. Pat. No. 5,815,227 discloses a backlight device used in a LCD. The backlight device comprises a light-inducing plate installed on the bottom surface of the LCD, a lamp installed on one side portion of light-inducing plate, and a lamp cover enclosing a part of the outer circumferential surface of lamp for reflecting the light from the LCD to light-inducing plate, wherein the light-inducing plate and lamp cover are directly coupled with each other by a locking structure. The locking structure is comprised of a locking protrusion formed on at least one of the upper and bottom surfaces of light-inducing plate and a locking hole in a corresponding portion of lamp cover. The lamp is fixed by locking the corresponding locking protrusions and locking holes.
U.S. Pat. No. 5,280,372 discloses a back light device built in a compact LCD device. The back light device comprises a light transmitting plate disposed behind a liquid crystal element, a light source disposed in the vicinity of one end of the light transmitting plate, a reflector for reflecting light from the light source towards the light transmitting plate, and a frame for supporting the backlight device. The light source may use a cold cathode tube (CCFT). Both ends of the light source are protected by a resinous protection member. The light source is supplied electric power through a corresponding lead wire and connector.
The light source and the reflector construct a side-slidably light source unit. The backlight device comprises a slide mechanism. The slide mechanism includes a guide rail fitted to an end of the frame. One end of the guide rail is made open so that the reflector is slidably along the guide rail. Therefore, a failure CCFT can be replaced by detaching the light source unit through the slide mechanism. The light source unit can be installed back to the backlight device after replacing with a new CCFT.
In the aforementioned conventional arts, the light source unit only comprises the mechanism for fixing light source without a positioning structure. The light source is easily tilted without the positioning structure so that the optical performance is degraded.
Furthermore, there is a need to replace the failure lamp or tube in the backlight device of LCD. The lead wire and a fixed tape for fixing the lead wire are easily scraped by the frame or back panel of LCD so that a Hi-Pot test will be failed or the fixed tape will be rolled.